Thermostatic switch



April 21, 1953 J. B. cATALDo 2,636,098

THERMOSTATIC SWITCH Filed May l, 1950 2 SHEETS-SHEET l .-e 2a l! I N V EN TOR. JO//A/ 5. @Q7/4x00 April 21, 1953 J. B. cATALDo 2,636,098 THERMosTATIc swITcH Filed May 1, 195o 2 sHEETshSHEET 2 1:1 E JN'VENTOR. I Ja//N CHT/4L 0o Patented Apr. 21, 1953 THERMOSTATIC SWITCH John B. Cataldo, Bernardsville, N. J., assignor to John B. Pierce Foundation, New York, N. Y., a

corporation of New York Application May 1, 1950, Serial No. 159,250

9 Claims.

This invention relates to thermoresponsive switch devices and more particularly to improved thermostats and circuit breakers utilizing snap spring members.

In a conventional thermoresponsive snap switch or circuit breaker assembly affording snap control, the thermoresponsive member is mounted adjacent an electrical resistance heater designed to carry :a current which is a function of a load current. Preferably the heater element is spaced from the thermoresponsive element in order that the heater might not interfere mechanically with the action of the snap element. In such case the rate of heat transfer to the Isnap element is limited by this spaced relationship and, in addition, the size of the assembly is increased because of the extra depth required to house the spaced elements.

It is also conventional to pass load currents directly through a thermoresponsive snap member as a means of heating the member to induce snapping. Because the resistance value of the snap member is inherently low, units of this design necessarily have high current ratings or low sensitivity. Moreover, a snap spring member may not be made to provide any given resistance value over a wide range without impairing the snapping properties thereof.

It is accordingly an object of this invention to provide a thermostat switch which is designed to provide greater sensitivity as a circuit breaker and `also to provide an economical and integrated unit whereby various trip ratings may be attained over a wide range without jeopardizing the snap characteristics of the thermoresponsive member.

It is another object `of the invention to provide a thermoresponsive snap switch assembly which may be adapted to meet either high or low load current ratings within close tolerances.

It is still another object of the invention to provide a thermostat or a circuit breaker device affording snap control action wherein the rate of heat transfer between the heating element and the lsnapping element is greatly increased.

According to the invention a bimetallic snap disc or other thermoresponsive snap element is formed as an integrated unit with a heater `element, the snap element and heater being separated by suitable insulating means to dene the electric circuit. The electric circuit may be formed either independently of or in combination with the bimetallic snap member as may be required to achieve various rating characteristics. In one embodiment of the invention a' (Cl. ZOO- 122) series circuit is established including the heater strip and the snap member, thus assuring a current path oi' maximum length through both com ponents. The heater element is preferably formed of a flat strip material which, as compared to conventional heater wire, affords greater heat transfer from the heater to the disc. Hence, lower current ratings may be attained than would be possible using heater wire of the same electrical characteristics.

The above and other objects of the invention will be apparent from the following detailed description of thermoresponsive devices formed according to the invention taken in conjunction with the accompanying drawings, in which Fig. 1 is a plan view of a thermoresponsive lsnap switch assembly;

Fig. 2 is a view in cross-section of the switch assembly shown in Fig. 1 taken on the line 2 2 thereof looking in the direction of the arrows;

Figs. 3 and 4 are plan views of slightly modifled forms of the thermoresponsive vdevice shown in Fig. 1;

Fig. 5 is a fragmentary view in cross-section of an alternative method for afxing electrical contact elements to the moving or snapping portion of the assembly;

Fig. 6 is a plan view of a modied thermoresponsive device embodying the invention;

Fig. 7 is a view in cross-section of the assembly shown in Fig. 6 taken on the line 1 1 and looking in the direction of the arrows, and

Figs. 8 and 9 are lplan views loi" possible modiiication of the switch assembly shown in Fig. 6.

Referring to Figs. l and 2 of the drawing, the invention will be seen as embodied in a thermoresponsive snap switch assembly comprising a conventional bimetallic four-legged snap disc I0 centrally mounted on a stationary post II by means of a central aperture formed in hub portion IUa of the disc. Surmounted upon the snap disc I0 is a strip resistor element I3 having 'a iiat cross-sectional contour and an S conguration in plan view, the strip being formed on its extremities with turned or folded ears III and I5 underlying the periphery of the disc I0.

The resistor or heater strip I3 is insulated from the disc I0 by a relatively thin insulating sheet I6 formed generally in the same coniiguration as the heater strip I3 and made of coarsely woven glass mesh or yother suitable non-conducting material. The insulating sheet I6 also underlies the snap disc I0 in the vicinity of the turned ears III and I5 in order to prevent contact between the .disc and heater at those points. Secured on the under surface of the ears I4 and I5 respectively are a pair of electrical contact elements I'I and I8.

The laminated assembly, comprising the snap disc I0, the strip heater element I3 and the in sulating strip I6, is centrally apertured and received on the post II where it is embraced by a pair ci lock-nuts ISthreaded/'on'thepost. The resulting in-tegratedf'assembly is suchy that itsl peripheral portions may partake of snap action under the influence of heat on the thermoresponsive snap disc, the latter being adaptedtosnap between two configurations of equilibrium as shown in full and dotted lines' in z-Fig. 2,. carrying with it the flexible heatery stripand. insulating@ sheet in concurrent movements.

For detailed disclosures ofA ,-thermoresponsive snap members of the type contemplated in this invention reference may be had to the following pending U. S. patentapplications: Serial No.

1-.i628g441jled November A ,1 4',f,1945, entitled .T Oggle YSprings, now` Patent No.. 12,571 ,1' l0,=, dated rOctober 16; 1951; Serial;Noiigfiled December-y19, :1945,- entitled Snap DiscvSpringsnoW Patent No. .;2,'604,316,; dated ;July..22, 1952 andY Serial No. 139,182, filed.- January H18; f 1950;,- entitled: Snap Springs and .Methods ofi-Manufacture.

The post `I I is rigidly supportedin a mounting plateiZIl formedjof insulating?materialgthe;plate being centrally apertured toA receive A,thepost andv a pair of lock-nuts ZI being providedas aconvenient means for. vanchoring thelatterftherein.

' The-mounting l platerl. is also formed withf aper- 'vv-tures 221and 23A underlying .the ,respective electricalcontacts i I'I and 5I 8. carried. adjacent the `periphery of the snap disc, anda pair. of terminal bolts 24 and 25 are received ink-theaperturesZZ `and 23 respectively. l'The. bolts 24.and"25. are kformed vwith enlarged head :portions rt and 21 respectively which comprise stationary electrical contacts, the upper surfacesof which are adapted tobe engaged bythe movable `contacts I-'I andIB respectively. Nuts 28 are threaded onto each kbolt -ZAand 25 to secure eachfof the latter in the plate 2l).` Suitable terminal l assemblies comprising a pair of washers229 and a nut13IIV follow the anchoring nuts 28 on the shank of each bolt to form suitable terminal connectors for receivingv lead wires (notshown).

An electrical circuit is-established'between the Aterminal posts including'y the l.stationary contact 25, the engaged movable contactI'I,l-therheater strip I3', movable contact I8 and stationaryfcon- ".tact 2l,- this circuitbeing-closed lat suchv times asthesnapdisc member'tl isfdisposedin its congurationof equilibrium'as shown in full lines in' Figzz and hereinafter termed cold position. In operation the current passing: through the hea-ter strip I3 will result in' the `generation of heat which will be eiiicientlyv radiated't'o .the snap disc I8 to induceI snapping of the latter, into its Ysecond configuration of equilibrium, 'thereby opening the electrical circuit. The design of the assembly may be suchk that this action occurs at any one of a wide range of predetermined currentl values: Withv the circuit opened the snap disc is permitted toy cool, after which' it may return automatically to the cold or circuit closed posi-tion. -If preferred however, the character- 'Mistics of the snap disc may be such that it will vnot return to its circuit-closed position Within the Vambient temperature. range inv which: the unit is to be operated, in whichcaseamanualreset operation is required.

i' In order to vary .the calibrationl characteristics of the unit the heater strip I3 may be varied in its configurations as shown in Figs. 3 and 4 wherein the total length of the strip element is changed to vary the resistance v-alue thereof.

If desired the movable contact assembly may be modified as shown in Fig. 5 wherein the heater strip I3 terminates on the upper surface of the `snapi disc adjacent the :peripheryz thereof. In

. such case supplementary conductive lugs 3l may be welded, riveted or otherwise secured to terminal ends of the resistor strip I3, with the mov- .able contact II being aiiixedto the supplementary member 3l as shown.

q v,In ordertoincrease the sensitivity or decrease theload current rating of a unit formed according to Athe invention, the embodiment thereof as shown in Figs. 6 through 9 may be utilized. As

shown in Fig. 7, the mounting plate 2E! and stationary contact assemblies 26 and 2l as well as the mounting post I I are all substantially similar ,-tofthestructure ,shown-in Fig-2 and described above.: The; snap: spring disc and vrheater assem- -fbly however are modified to Yprovide an electrical circuit in which the heater stripandgsnap. spring .disc are connectedin a series circuit so that the loadcurrent Vmay flow throughweach rinseries,

. rthereby to increasethe heating eiiciency ofthe unit. Y The. modified assembly includesL a snap spring disc I0 ofathesame typedisclosedabove centrallyapertured and received on a shouldered r.insulatingwasher 32, Whichis in turn fitted over fthe mountingposttI I.` A heater strip '33,is sur- Vmounted on the discll ioriiexingmovement in unison therewith, thefheater strip 33 being aperltured at its central portion to abutthe, outermost sifioulderfofl the insulating.,.washerf -32 and with the insulating sheet Ibeing sandwiched-between the disc and the heater as'descri-bed above.L One turned-underv ear4 portion V311 V.carrying a Vmovable Y v contact 35, whilefthe other terminus of the-heater 33 is spot-welded at`36- (Fig. 6) to-form an electrical connection with the, snap dischIIl.

' The; shouldered insulating washer 32 `insulates thefresistance strip heater .S3-from, the post II s to preventan electrical short-circuit. between `the discand heater ythrough the'centerl-post II. A

movable contact element' 3l, having an extended shank portion.Y 3S to bring it into alignment-with contact 35, is secured to the ,disc vI.-1In,this

g 1 embodiment of the invention, an felectrical cir- V'cuit is-setup between the stationary contacts `25 ,andfZ including, in series, the VE-shaped*resistor stripSS, the weld-connection 36, the snapzdisc IB and the contacttl. ,In `.this fashion the heating eiciency of the load current is increased,

Ythereby to provide a thermoresponsive unit of lower current rating.

Y In order to vary the effective heating-properties of the assembly the planrviewcongurations ofthe heater-strip 33 may be varied as shown inFigs. 8 and 9, .these variations alfordingdifferentresistance vvalues -for the circuit andi'hence vchanging the operatingorresponse characteristics of the assembly.

Changes may be eected in the ratingsof the various assemblies,y disclosed herein-by. (1) changing the basic trip temperatureof` the-bimetallic snap discsl Iii, all as set forth in the copending U. S. applications above referred to;4 (2) chang- `'ing -thewidth, thickness-'and length 'of the strip heatermembers and (3)changingv the proxim- Y*ity of the heater strip of the-'snap disc `in order to vary thelheat transfer characteristics therebetween. Ingenerahan increase, of the opposing surface areas between the heating rstrip and disc Will facilitate more rapid transfer of heat and will decrease the current rating of the assembly.

From the foregoing disclosure it will be apparent that numerous modifications may be made in the various units formed according to the invention without departing from the spirit and scope of the invention, and accordingly the invention should not be limited save as set forth in the following claims.

I claim:

1. In a thermoresponsive snap switch assembly, a thermoresponsive snap spring member adapted to snap between two configurations under the influence of heat, a fiat flexible strip heater element having a given electrical resistance value disposed in close proximity to said snap member for flexing movement in unison therewith, said strip heater being substantially rectangular in cross section and having its large area opposing the surface of the said snap spring member, means insulating said snap spring member from said heater element at at least one terminus of the heater strip and throughout the length of the heater strip between the termini thereof, and a plurality of electrical contact means electrically connected respectively to the termini of said heater strip.

2. A thermoresponsive snap switch assembly including in combination a thermoresponsive snap spring member adapted to snap between two configurations of equilibrium under the influence of heat, a heater strip comprising a fiat strip element superimposed on said disc in close proximity thereto for flexing movement in unison therewith, means supporting said heater and snap member to afford snap movement between said configurations, means providing an electrical connection between one terminus of said strip and said snap member, first contact means electrically connected to the other terminus of said heater strip adjacent a moving portion of said disc, a second electrical contact mounted on said disc and electrically connected thereto at a point of movement of said disc and spaced from the first contact means, means providing electrical insulation between said strip and disc at all points except the electrical connection therebetween and stationary contact means positioned to be engaged by the contact mean-s on the snap member and the contact means on the heater strip to provide a series circuit therebetween including the heater strip and at least a portion of the snap member.

3. A thermoresponsive snap switch assembly including in combination, a bimetallic snap spring member adapted to snap between two configurations of equilibrium under the influence of heat, a fiat resistance strip heater formed of flexible material and overlying Said snap spring member in close proximity thereto, a thin insulating strip disposed between said strip heater and said member, mean-.s securing said strip heater and said member for unison movement relatively to said mounting post, and electrical contact means movable with said snap member and electrically connected to said heater strip at its respective termini, at least one of said contact means comprising an extension portion adjacent one terminus of the heater strip and adjacent the periphery of said snap spring member, said extension portion being looped over the periphery of the snap member.

4. A thermoresponsive snap switch assembly including in combination a mounting plate, a

post carried by said mounting plate, a bimetallic snap spring member centrally mounted on said post and adapted to have its peripheral portions snapped between two configurations of equilibrium under the influence of heat, a flat strip heater disposed in laminated relationship to said snap member for movement in unison therewith, insulating means separating said heater strip and said member, a looped portion formed at one end of said heater strip to overlie the periphery of said snap member and a looped portion formed on the other end of the heater strip to overlie the periphery of said snap member at a point spaced from said first looped portion, and electrical contact means carried by said looped portions.

5. In a thermoresponsive snap switch assembly including in combination a mounting plate, a post carried by the plate, a bimetallic snap spring member adapted to snap between two configurations of equilibrium under the iniiuence of heat and centrally apertured to receive said post, a flat resistance heater strip formed of flexible material and overlying said snap spring member in close proximity thereto, a thin insulating strip disposed between said heater strip and said snap spring member, means securing the heater strip and snap spring member for unison movement relatively to said mounting post, electrical contact means movable with said snap spring member and electrically connected to said heater strip adjacent its respective termini, stationary contact means carried by said mounting plate and adapted to be engaged by said movable contact means when the snap spring member is in one configuration of equilibrium, said heater strip and snap spring member are formed with aligned apertures to receive said mounting post, and clamping means for securing said heater strip and snap spring member rigidly with respect to said post adjacent said apertures.

6. In a thermoresponsive snap switch assembly, a mounting plate, a supporting post carried by said mounting plate, a snap member formed of bimetallic material and adapted to snap between two configurations of equilibrium centrally mounted on said post, a flat resistance strip heater disposed in laminated relationship to said member for movement in unison therewith and insulated from said snap member at all points except one terminus of the latter, means forming an electrical connection between said one terminus ofthe heater strip and said member, a contact element carried by said member and electrically connected thereto, and a second contact element connected electrically to said heater strip, and insulated from said member to establish a series circuit between said contacts including the strip heater and at least a portion of said member.

7. In a thermoresponsive snap switch assembly as set forth in claim 6 including clamping means carried by said supporting post for securing the said flat resistance strip heater thereto adjacent the center of said snap member, said strip heater and member being electrically insulated at said supporting post.

8. A thermoresponsive assembly comprising a bimetallic snap spring member adapted to snap between two congurations under the influence of heat, a flexible heater element, first means attaching said heater element to the snap member adjacent the termini of the heater element. second means attaching said heater element to the snap member at at least one point between thezheater terminitsaidlbeater; element-thereby beingv .mounted forexing, movement in v unisonY with saidj snap member, means insulating said heater element from said `snap spring member att at least one terminus ofthe heater strip and throughoutsubstantiallythe f ulllength of the heater element between its termini,- and eleotrioalxcontact means...electrically connected' to they heater elementV adjacent the respective Yter miniV thereof.-

9. A thermoresponsive assembly comprising-.a bimetallic -snap;spring member adapted tofsnap between two configurations under the inuence oi-heali a flat, exible heater strip elementattached. toV said member and disposed' inV close proximity thereto for iiexing movement in unisonn therewith, means-.insulatingsaid heater element fiomaid.snapspring member at at least one terminus'of the heater element and throughout substantially the. full length of the heaterv e1e ment.- between litstermini, and electricalv con-V tact means electrically connected to the termini of said heater'element, at least one of said contact means comprising an assembly including an extension portion adjacent one terminus of the heater element and adjacent the periphery of said snap spring member, said extension portionfbeing looped over the periphery of the snap member:-

JOI-IN B. CATALDO.

References. Cited: theiileofths patent UNITED STATES PATENTS Number Name. Y Date 1,664,2014 Fay Mar. 27, 1928 2,011,610 Bletz .Y Aug. 20, 1935 2,199,387 Bolesky May "1 1940 2,293,179 Swingle Aug. 18, 1942 2,518,941 Satchwell et al. Aug. 15, .1950 

